Amino
acids are the foundation upon which life
is built. Proteins are formed from these
compounds and cannot exist nor carry out
their work without the proper combination
of amino acids. After water, protein is
the second most plentiful substance in the
human body.
There
are approximately twenty-nine commonly known
amino acids that account for the hundreds
of different types of proteins present in
all living things. The liver produces about
80 percent of the needed amino acids; the
remaining 20 percent must be obtained from
outside sources. Essential amino acids are
those which cannot be synthesized within
the body and must be obtained through dietary
sources.
The
essential amino acids are: isoleucine, leucine,
lysine, methionine, phenylalanine, threonine,
tryptophan, and valine.
Those
amino acids which can be synthesized internally
by the body are considered nonessential.
The
nonessential amino acids are: aspartic acid,
asparagine, glutamic acid, glutamine, glycine,
proline, serine and tyrosine.
Arginine
and histidine are labeled semi-essential
because they do not fall perfectly into
either of these categories. They become
essential during times of growth, when the
body cannot produce them in adequate amounts.
Amino
acids are referred to by their prefixes
L- (for levorotatory, or "left-handed"),
or D- (for dextrorotatory, or "right-handed"),
indicating slight differences in molecular
structure. L-series amino acids are in the
same form as amino acids in plant and animal
tissue, and are much more common than either
the D- form or the mixed DL- form.
